414 A MANUAL OF ANATOMY 



to the inner and back part of the arm. The lateral cutaneous branches of the 

 succeeding intercostal nerves are to be shown in two divisions — anterior and 

 posterior. The axillary glands are to be carefully looked for. They will be 

 found in three groups, namely, pectoral, within the anterior fold and on the 

 adjacent part of the inner wall ; subscapular, on the posterior wall ; and external, 

 on the outer wall. The posterior thoracic nerve is to be followed out upon the 

 serratus magnus, the long thoracic artery will be found along the lower border 

 of the pectoralis minor, and the subscapular artery on the posterior wall. 

 The dorsalis scapulae branch of the subscapular artery is to be shown. The 

 alar thoracic is seldom a special artery. The middle or long and lower sub- 

 scapular nerves will be found on the posterior wall, the former, with the 

 subscapular artery, going to the latissimus dorsi, the latter, farther out, 

 supplying the teres major and adjacent part of the subscapularis. The upper 

 or short subscapular nerve should not be looked for at present, as it Ues too 

 high up. The structures along the outer wall are next to be shown, namely, 

 the axillary artery, giving off its subscapular, anterior circumflex, and posterior 

 circumflex branches ; the axillary vein ; and the nerves arising from the cords 

 of the brachial plexus. The internal cutaneous branch of the musculo-spiral 

 nerve should be shown at this stage, and preserved. When the tributaries 

 of the axillary vein have been noted in the course of the foregoing dissection 

 they should be removed. 



The sterno-costal portion of the pectoralis major is now to be divided and 

 reflected, in doing which twigs of the internal anterior thoracic nerve will 

 be seen entering its deep surface, after having pierced the pectoralis minor. 

 The latter muscle is now to be dissected, the fascia, removed in preparing it, 

 being continuous above with the costo-coracoid membrane, and being inserted 

 below into the upper surface of the axillary fascia. The internal anterior 

 thoracic nerve is to be shown entering the deep surface of the muscle. The 

 pectoralis minor having been cut, the axillary space will be fully exposed. The 

 second part of the axillary artery is to be dissected, and it will be found, as 

 a rule, to give off the long thoracic, but the alar thoracic is very inconstant. 

 The cords of the brachial plexus and their relation to the second part of the 

 artery are to be noted, and the upper or short subscapular nerve may now 

 be seen at the upper part of the posterior wall of the space, where it immedi- 

 ately enters the upper part of the subscapularis. The origins of the branches 

 of the cords of the brachial plexus are to be shown as follows : external 

 anterior thoracic, musculo-cutaneous, and outer root of the median from the 

 outer cord ; internal anterior thoracic, lesser internal cutaneous or nerve of 

 Wrisberg, the internal cutaneous, inner root of the median, and ulnar from the 

 inner cord ; and the three subscapular nerves, circumflex, and musculo-spiral 

 from the posterior cord. 



The next duty of the dissector is to study the sterno-clavicular joint. There- 

 after the clavicle is to be sawn through at its centre, and tlie subclavius muscle 

 divided. At this stage the dissectors of the upper limb and head should work 

 in concert. A full view will be obtained of the continuity between the sub- 

 clavian and axillary arteries, and the nerve trunks and individual nerves of 

 the brachial plexus, as well as the supra- clavicular branches of that plexus. 

 The suprascapular artery and nerve, and the posterior belly of the omo-hyoid 

 will also be seen. The vessels and nerves are then all to be included in two 

 ligatures placed i inch apart, and divided between them, and the lower ligature 

 is to be firmly secured to the outer cut end of the clavicle. The serratus magnus 

 is to be studied, and it will be put upon the stretch if the shoulder is pressed 

 outwards. The limb is then to be removed by dividing the serratus magnus, 

 posterior belly of the omo-hyoid, and levator anguli scapulae, if the latter has 

 not been already cut. 



Scapular Region. — After removal of the limb, the dissector is to trim the 

 various scapular muscles already dissected, and the arrangement of the tendon 

 of insertion of the pectoralis major is to be shown. The shoulder being sup- 

 ported on a block, the skin is to be removed from over the deltoid, and the 

 cutaneous nerves shown, namely, the su])ra-acromial over the upper third, 

 and a large cutaneous branch of the circumflex turning round the postcriui 



